packages.mk: update several packages

Update the following packages to their recent versions:

    Lua (5.2.2)
    Git (1.8.4)
    GCC (4.8.2)

Encode inline patches using base64 to avoid inconsistencies with regard to
escaping with different versions of GNU make.

Install GMP header files to include directory for GCC plugins. Retrieve
GNU MP from http mirror.

The update follows git://git.colberg.org/packages.git, which is
maintained by Peter Colberg.
packages.mk: fix lib path in GCC prerequisites

If libdir is omitted during configuration, it is either lib or lib64
depending on the architecture. Then packages depending on GMP, PPL, ...
do not find the respective libraries.

The issue appeared on OpenSuSE 12.3 and may be related to
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53798.

In cloog-ppl, adding linkage against libm.a resolved the following
error:

ld: .../.ppl-0.11.2/lib/libppl.a(Init.o): undefined reference to symbol 'fegetround@@GLIBC_2.2.5'
ld: note: 'fegetround@@GLIBC_2.2.5' is defined in DSO /lib64/libm.so.6 so
try adding it to the linker command line
/lib64/libm.so.6: could not read symbols: Invalid operation